This invention relates to a device and a method for the separation of orientable or deformable particles. In particular it relates to a device which uses a radial migration technique to separate orientable or deformable particles such as large polymer molecules.
It has been found that separation of large polymer molecules becomes increasingly difficult as the molecular weight increases. Such conventional techniques as sedimentation through the use of a centrifuge or by gel electrophoresis are not satisfactory with polymer molecules of very high molecular weight. In particular, random coiled DNAs have anomalous sedimentation coefficients making separation impractical in the centrifuge. The inhomogeneity of the gel structure limits gel electrophoresis to separations of molecules which have a molecular weight less than 5.times.10.sup.8 Daltons, with resolution at the upper end being relatively poor. While some efforts have been made in automated sorting of individual chromosomes, the procedure is a one-at-a-time effort which militates against its practicality for preparation of large quantities of such polymer molecules as DNA.
The deformability of very large macromolecules such as DNA and other molecules of chromosomal size has been at the heart of the separation problems mentioned above. This deformability manifests itself in dilute solutions of the macromolecules as viscoelasticity, a rather unusual set of properties when compared with ordinary viscous solutions. One property is the "Weissenberg effect." The Weissenberg effect occurs when a viscoelastic liquid is sheared in the gap between two moving surfaces such as concentric cylinders. In an ordinary viscous solution, the pressure is highest at the outside cylinder because the liquid is thrown to the outside by inertia. When a viscoelastic liquid is similarly sheared, the liquid will creep up the inside cylinder, and the pressure will be highest on the inside cylinder. A simple explanation is that the very large macromolecules act like elastic bands moving along circular flow lines between the cylinders. Since the relative motion of the two cylinders applies a shear force in the solution which stretches the molecules, there is a small component of tension in the molecule that acts to produce on the molecule an inwardly directed radial force. The sum of these radial forces from all the polymer molecules gives the Weissenberg pressure.
While the Weissenberg effect has been known for a long time, no practical use of the migration accompanying the Weissenberg effect has been made. Concurrently, the increase in research in large and very large macromolecules, with particular emphasis on DNA and the like, coupled with the knowledge that single DNA molecules may constitute whole chromosomes, has resulted in efforts to solve separation problems related to experimentation with such macromolecules.
It is therefore an object of this invention to provide a device for separation of large to very large macromolecules utilizing a radial migration principle.
It is another object of this invention to provide a method for separation of large and very large macromolecules through the principles of radial migration.
It is also an object of the invention to provide a separation device for large and very large macromolecules that is relatively inexpensive.
It is still another object of this invention to provide a device that separates large and very large macromolecules so that the user is confident that separation of the molecules has occurred.